:active and activating via the keyboard

[domenic]

Spinning off from #6635 (comment) . Question: when does :active match? #7465 takes care of some of the current interop problems, but isn't merged yet due to lack of tests; let's use https://whatpr.org/html/7465/semantics-other.html#selector-active as the working definition for this issue.

https://jsbin.com/cifugag/1/edit?html,output shows that the spec does not match either Firefox or Chrome:

• Spec: pressing spacebar on the <input type=radio> must not match :active, since it's not on the special list of elements for which "in a formal activation state" applies. Pressing spacebar on the <button> must match :active, since it is on that list.

• Firefox: pressing spacebar never causes any elements to match :active. Only the "being actively pointed at" clause applies.

• Chrome: pressing spacebar causes both the <input type=radio> and the <button> to match :active. It does not cause the <div> to match :active. Chrome appears to be applying the "in a formal activation state" definition to any element with activation behavior, which includes radio buttons but not divs.

• Safari: ???

I personally think the Chrome behavior makes the most sense (as it gives keyboard users and mouse users the same experience). The next step is to test Safari to see if that can give us any input.

[domenic]

The "normal a" link in https://output.jsbin.com/hujeguhivo throws a wrench into this ontology. Apparently keydown on the Enter key will navigate a link, and will not cause that link to match :active. So there's no "in a formal activation state" for <a> elements, really. Fun...

[emilio]

Ah, I was going to file an issue about this stuff because @dshin-moz and I were looking at some :has() interop-2023 failures, and found yours, @domenic :)

Other things that are funny about this:

• On WebKit and Blink, :active on buttons doesn't propagate the active state through the ancestor chain. test case
• On WebKit and Blink, if you preventDefault() the keyup event, the :active state persists. test case
• The timing at which the flag is set and cleared is not interoperable either, even on click. test case. @mfreed7 do you know when stuff is set / unset in Blink?

It'd be nice to get better spec text for how this is supposed to work... cc @smaug----

[mfreed7]

• The timing at which the flag is set and cleared is not interoperable either, even on click. test case. @mfreed7 do you know when stuff is set / unset in Blink?

The behavior of :active is definitely odd and could use some attention. I know Blink has several bugs in this area. The code is this one, calls to which are sprinkled everywhere.